Final answer:
The speaker did not perform any of the actions listed in the question; they studied for an exam and walked back to their apartment. No definitive answer can be provided without additional context.
Step-by-step explanation:
Based on the given reference texts, the speaker did not perform any of the provided actions after walking back to the school. Instead, the speaker describes leaving the library, retracing their path back to their apartment, and studying for an exam. There's no mention of sitting for two days, looking for someone named Isaac in the woods, or wandering around the school campus. Therefore, without further context, it is not possible to provide a definitive answer to the given multiple-choice question. If the question is in relation to a specific piece of literature or text, that source would need to be consulted to provide an accurate response.